The interaction between Ag+ and human serum albumin (HSA) has been intensively studied by means of equilibrium dialysis, ligand-to-metal charge transition (LMCT) bands, circular dichroism (CD) and Raman spectroscopy. Scatchard analysis of the results of 1 equilibrium dialysis indicates the presence of two types of binding sites for Ag+ on HSA, and the orders of magnitude of binding stability 54 constants are found to be 10 5 and 10 4, respectively. During the binding process, a gradual increase in absorbance values of LMCT bands is observed with time-scanning UV absorption spectra, implying the Ag(Ⅰ) centers are continually formed in HSA. The time-scanning CD1 spectra provide evidence that the binding of Ag+ induces HSA to undergo a slow rearrangement of tertiary structure, and to change from 11 the original conformation in the absence of Ag (B-state) to conformation binding with Ag (A-state). The rate constants and activation free energy of A-B transition are calculated. The Raman spectrum of Ag(Ⅰ)-HSA system shows distinct vibration bands at 224 and 246 21cm in the low-frequency region, which significantly reveal the formation of Ag-S and Ag-N bonds. In addition, the electrostatic 1 interaction between Ag+ and negatively charged oxygen is also detected with Raman spectroscopy.